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Recycling of waste tires is the goal of many studies, where the chemical dissolution method depends on the recovery of tire rubber (TR) and carbon black (CB) from the waste tires. Petroleum ether was used to dissolve tire powder and a black solution was produced which after refluxed at 140°C for two hours with a mixture of adsorbents including silicon dioxide (SiO2) and aluminum oxide (Al2O3) and then filtered, will give clear rubber filtrate and CB precipitate and the used petroleum ether was totally regenerate. The rubber was recovered with a weight percentage of 24% (w/w), whereas CB was reclaimed with 20% (w/w) from the total waste tire used. The recovered rubber was characterized and its functional groups were studied by 1H-NMR and FTIR spectroscopy which shows the rubber is polyisoprene blended with polybutadiene. The XRD, FESEM, and thermal analyses (TGA, DTA, and DSC) show the recovered rubber is amorphous with an elastic nature, thermally stable with endothermic behavior, and contains some inorganic impurities. On the other hand, the BET (Brunauer-Emmett-Teller) analysis, of carbon black shows it is a mesoporous material with a high specific surface area (as = 149.44m² . g -1) and pores with a mean diameter (13.623 nm). The particle size, structure and surface chemistry of the reclaimed CB which was measured accordingly by XRD, BET, and FESEM and it was emphasized that the CB has excellent adsorption qualities. Keywords: Recycling of tires, rubber, petroleum ether, carbon black, Silicon dioxide, Aluminum oxide. [ABSTRACT FROM AUTHOR]

The paper presents an analysis of the filler's effect on the machining process and on changes in the thermomechanical properties of polymer composites based on aluminum chips. Composite research samples with a polymer matrix in the form of polyamide 6 were made by the pressing method. Comparative studies were carried out on the changes in thermomechanical properties and structure of the obtained molders with different filler contents and different fractions after the machining process. In order to determine the changes in thermal and mechanical properties, analysis was carried out using the differential scanning calorimetry (DSC) method, thermal analysis of dynamic mechanical properties (DMTA) and a detailed stereometric analysis of the surface. After mechanical processing, roughness amplitude parameters and volumetric functional parameters were determined. In order to analyze the structure, tomographic examinations of the manufactured composite were conducted. In relation to the polymer matrix, a significant increase in the storage modulus of the composites was noted in the entire temperature range of the study. An increase in the enthalpy of melting of the matrix was noted in composites with a lower filler content and a shift in the melting range of the crystalline phase. Significant differences were noted in the study of the composite surfaces in the case of using fillers obtained after machining with different fractions. The dependencies of the functional and amplitude parameters of the surfaces after machining of composite samples prove the change in the functional properties of the surface. The use of aluminum chips in the composite significantly changed the surface geometry. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) modules are a key technology to aid the imminent transition from carbon‐based energy. End‐of‐life crystalline silicon PV modules produce a waste stream that is predominantly landfilled due to the recycling challenges associated with PV reuse economics. Current practices recycle the aluminum frame and repurpose the junction box but landfill the rest of the module. The primary challenge in recycling the remaining module is finding a technoeconomically viable method for separating the silicon and glass from the ethylene vinyl acetate (EVA) layers. This issue will rapidly expand with time as it is estimated that flat glass production for solar panels is currently unable to meet the demand for PV. Current literature suggests that chemical, thermal, and mechanical delamination offer economically feasible solutions under ideal circumstances. In this work we evaluate these methods using end‐of‐life panels and assess the economic viability. The technoeconomic study presented here suggests the most economically viable option for disposing of end‐of‐life solar panels, given current technology, is landfilling. Thermal delamination may offer an alternative route in the future. Financial incentives, which can be quantified with this work, may be required to kickstart PV recycling to help bridge externalities around environmental impact. [ABSTRACT FROM AUTHOR]

Aluminum recycling is an important step to achieve high value-added utilization of fly ash to improve the leaching efficiency of Al. In this paper, Na2CO3 was used as the flux and HCl as the leaching solution to extract Al from CFA by using the roasting activation-acid leaching process to investigate the influencing factors of the leaching rate of Al to analyze the mineral composition of the roasting products explore the activation process of CFA roasting. The experimental results showed that compared with NaF, CaO, and NaOH, the highest Al leaching rate was achieved when Na2CO3 was used as a flux, at which time the leaching rate could reach up to 81.62%, and it was about 63% higher than that of extracting Al from the fly ash using direct roasting-acid leaching method. When the roasting time is 90 min, the roasting temperature is 850°C, the CFA/Na2CO3 is 1.5, the hydrochloric acid concentration is 4 mol/L, the acid leaching temperature is 90°C, the S/L is 1:4, and the maximum leaching rate of Al is 81.62%. According to the thermodynamic theory, Na2CO3 and mullite gradually reacted with each other above 800 K to form chalcopyrite, and Na2CO3 reacted with mullite and quartz in CFA to form chalcopyrite more easily. According to the reaction kinetic model, the acid leaching process of CFA is mainly controlled by diffusion, and a semi-empirical equation is proposed to describe the whole leaching process. [ABSTRACT FROM AUTHOR]

This study aims to identify the occurrence and characteristics of PCDD/Fs in soil and sediment samples from secondary copper and aluminum villages in northern Vietnam using the HRGC/MS system. Additionally, it assesses the impact of PCDD/Fs on human health and the potential ecological risks they pose. The residual concentrations of PCDD/Fs in soil and sediment samples collected from the secondary copper Dai Bai village and secondary aluminum Man Xa village were as follows: 0.37 ± 0.29 ng TEQ/kg d.w. (ranging from 0.06 to 0.63 ng TEQ/kg d.w.); 4.88 ± 0.51 ng TEQ/kg d.w. (ranging from 0.512 to 12.17 ng TEQ/kg d.w.); 11.2 ± 5.31 ng TEQ/kg d.w. (ranging from 5.12 to 15.2 ng TEQ/kg d.w.); and 21 ± 12.7 ng TEQ/kg d.w. (ranging from 0.37 to 31.6 ng TEQ/kg d.w.), respectively. The distribution of PCDD/Fs indicated Octa- and Hepta-CDD/Fs as the dominant congeners with high chlorine content. The TEQ levels of PCDD/Fs in all soil and sediment samples were found to be below the allowable limit according to Vietnamese regulations, with the top contributor being 2,3,4,7,8-PeCDF. Samples collected near the production areas exhibited higher levels of PCDD/Fs compared to those collected farther away. The UNEP toolkit was utilized to determine the permissible dioxin TEQ concentrations suitable for livestock farming. The lifetime average daily doses (LADD) of PCDD/Fs via soil ingestion in Man Xa and Dai Bai were calculated as 0.04 × 10−3 and 1.54 × 10−3 pg TEQ/kg d.w. respectively. The relative cancer risks for humans were estimated at 0.05 × 10−12 and 2.05 × 10−12. Furthermore, the ecological risk assessment method indicates that dioxin in all soil and sediment samples near the aluminum recycling craft village had a negative impact on the ecosystem. In contrast, sediment samples taken away from the aluminum recycling craft village and all sediment soil samples in the bronze casting village did not show negative impacts on the ecosystem. [ABSTRACT FROM AUTHOR]

Conventional aluminum recycling consumes a substantial amount of energy and has a negative impact on secondary alloys. To address this challenging topic, Friction Stir Extrusion has been patented, which represents an innovative solid-state recycling technique that enables the direct extrusion of components from recyclable materials. In recent years, developing simulation models for Friction Stir Extrusion has become essential for gaining a deeper understanding of its underlying physics. Simultaneously, control of the microstructure evolution of extruded profiles is required, as it has a considerable influence on mechanical properties. This research involves a single Lagrangian model, adapted for both the FSE and the traditional hot extrusion processes. The simulations explored various rotational speeds and feed rates, revealing significant effects on grain size and bonding quality. To this model were applied different sub-routines, to investigate the impact of the FSE process with respect to the traditional hot extrusion process in terms of energy demands, quality and microstructure of the extruded pieces. The findings demonstrated that optimal grain refinement occurs at intermediate rotational speeds (600–800 rpm) combined with lower feed rates (1 mm/s). The energy analyses indicated that FSE requires lower total energy compared to traditional hot extrusion, primarily due to the reduced axial thrust and more efficient thermal management. As a result, it was possible to ensure the ability of the developed simulative model to be fully adapted for both processes and to forecast the microstructural changes directly during the process and not only at the end of the extrusion. The study concludes that FSE is a highly efficient method for producing high-quality extruded rods, with the developed simulation model providing valuable insights for process optimization. The model's adaptability to various starting materials and conditions highlights its potential for broader applications in extrusion technology. [ABSTRACT FROM AUTHOR]

The growing use of aluminum and its compounds has increased the volume of aluminum waste. To mitigate environmental impacts and cut down on manufacturing expenses, extensive investigations have recently been undertaken to recycle aluminum compounds. This paper outlines the outcomes of a study on fabricating standard EN AW-2007 alloy using industrial and secondary scrap through continuous casting. The resultant recycled bars were analyzed for their chemical makeup and examined for microstructural features in both the cast and T4 states, undergoing mechanical property evaluations. The study identified several phases in the cast form through LM, SEM + EDS, and XRD techniques: Al7Cu2Fe, θ-Al2Cu, β-Mg2Si, Q-Al4Cu2Mg8Si7, and α-Al15(FeMn)3 (SiCu)2, along with Pb particles. Most primary intermetallic precipitates such as θ-Al2Cu, β-Mg2Si, and Q-Al4Cu2Mg8Si7 dissolved into the α-Al solid solution during the solution heat treatment. In the subsequent natural aging process, the θ-Al2Cu phase predominantly emerged as a finely dispersed hardening phase. The peak hardness achieved in the EN AW-2007 alloy was 124.8 HB, following a solution heat treatment at 500 °C and aging at 25 °C for 80 h. The static tensile test assessed the mechanical and ductility properties of the EN AW-2007 alloy in both the cast and T4 heat-treated states. Superior strength parameters were achieved after solution heat treatment at 500 °C for 6 h, followed by water quenching and natural aging at 25 °C/9 h, with a tensile strength of 435.0 MPa, a yield strength of 240.5 MPa, and an appreciable elongation of 18.1% at break. The findings demonstrate the feasibility of producing defect-free EN AW-2007 alloy ingots with excellent mechanical properties from recycled scrap using the continuous casting technique. [ABSTRACT FROM AUTHOR]

The use of multi-materials, in which a wide variety of materials are used in the appropriate places, is being promoted to reduce carbon dioxide emissions. In the multi-materialization of automobiles, steel-aluminum joints are widely used. Friction stir welding (FSW) is used for joining steel and aluminum. Because of the solid state and short joining time of the FSW, the thickness of the brittle intermetallic compound layer can be minimized and high-strength joining can be achieved. Meanwhile, since recycling aluminum greatly reduces carbon dioxide emissions compared to the production of new ingots, easy disassembly technology is required. In this study, fabrication of thin foaming agent sheet was attempted. Then, we attempted to realize easy disassembly of steel/aluminum joints by FSW, which can realize strong joints, by using foaming agent sheets that can easily introduce foaming agent on joining interface during FSW. It was shown that foaming agent sheet can be prepared by solidifying foaming agent and pore morphology stabilizer powders using spark plasma sintering. It was also shown that even if a foaming agent sheet was introduced at the joining interface and FSW was performed, good jointing can be achieved. In addition, it was found that the introduction of a foaming agent sheet and foaming at the joining interface can significantly reduce the maximum disassembly load with fracturing at the joining interface. The above results indicate that the use of a foaming agent sheet can easily add an easy-disassembly characteristic to the area near the joining interface in the FSW process. [ABSTRACT FROM AUTHOR]

Current recycling methods for the very popular lithium‐ion batteries (LIBs) focus mainly on recovering valuable metals such as cobalt and nickel for economic reasons. The cell casing components, which are mainly made of aluminum, can make a significant contribution to achieving political recycling targets. Mechanical processes are used to separate the casing components from the overall LIB material stream. The aluminum, copper, steel, and plastic components are then further concentrated into various potential products by, e.g., magnetic separation, eddy current separation, and air classification. Considering the benefits of additional stress to compact the metal parts, the knowledge gained from the individual sorting steps can be combined to form a process flow chart. [ABSTRACT FROM AUTHOR]

Ni and Co elements in superalloy scraps are scarce metal resources in China, and recycling these metal elements has great environmental and economic significance. This present study proposes a novel and efficient recycling process for the recovery of nickel and cobalt elements from superalloy leaching solution. The superalloy leaching solution reacted with NaOH solution to obtain precipitates. Then, the precipitates were mixed with Na2CO3 and roasted at high temperature. After sodium roasting, Al and Cr elements were removed by water leaching to obtain pure NiO and CoO as raw materials for preparing ternary precursors. As the nuclear part of this process, the impacts of sodium roasting on the water leaching behaviors of Al and Cr elements from Ni and Co sediments was investigated. Under suitable conditions of sodium roasting, the leaching efficiencies of Al and Cr elements are 99.11% and 99.39%. Moreover, the promoting mechanism of sodium roasting on leaching of Al and Cr elements was discussed from the view of phase composition. [ABSTRACT FROM AUTHOR]

This work focuses on the recycling of aluminum-based metal joinery waste in the context of the treatment of wastewater containing organic materials, such as dyes, by electrocoagulation (EC); aluminum scraps were used as electrodes to process synthetic solutions of the methylene blue (MB) dye. The study investigated the effect of different parameters, including pH (3, 4, 5, 7, 9, 11) current density (100, 150, 200, 250 A/m² ), electrolysis time (30, 60,120 min), sodium chloride concentration (0.5, 1, 2 g/L) and the initial dye concentration (10, 20, 45, 60 mg/L) on the removal efficiency of MB. The results showed that the optimum conditions for MB removal were achieved at the original pH of the solution which is 7 using a current density of 200 A/m² and an inter-electrode distance of 1 cm with 10 mg/L as a dye concentration and 2 g/L of electrolyte. The removal efficiency under these conditions can reach 97.81 %. An estimation was made of the electrical energy needed to attain the ideal removal, which was found to be approximately 0.97kWh/g removal dyestuff the electrode consumption was 0.13 (kgAl /g of dyestuff), with an operation cost of 0.106 ($/g of dyestuff). The study suggests that EC using only two aluminum electrodes is efficient technique for the removal of MB from synthetic wastewater. The removal of the dye was monitored by UV–visible spectroscopy and scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) is used for the identification of the functional groups of MB in the obtained sludge by the EC process; and the aluminum electrodes surfaces, before and after treatment, were characterized by scanning electron microscopy (SEM) and Dispersive Energy Spectroscopy (EDS). [ABSTRACT FROM AUTHOR]

Aluminum electrolyte is a necessity for aluminum reduction cells; however, its stock is rising every year due to several factors, resulting in the accumulation of solid waste. Currently, it has become a favorable material for the resources of lithium, potassium, and fluoride. In this study, the calcification roasting–two-stage leaching process was introduced to extract lithium and potassium separately from aluminum electrolyte wastes, and the fluoride in the form of CaF2 was recycled. The separation behaviors of lithium and potassium under different conditions were investigated systematically. XRD and SEM–EDS were used to elucidate the phase evolution of the whole process. During calcification roasting-water leaching, the extraction efficiency of potassium was 98.7% under the most suitable roasting parameters, at which the lithium extraction efficiency was 6.6%. The mechanism analysis indicates that CaO combines with fluoride to form CaF2, while Li-containing and K-containing fluorides were transformed into water-insoluble LiAlO2 phase and water-soluble KAlO2 phase, respectively, thereby achieving the separation of two elements by water leaching. In the second acid-leaching stage, the extraction efficiency of lithium was 98.8% from water-leached residue under the most suitable leaching conditions, and CaF2 was obtained with a purity of 98.1%. The present process can provide an environmentally friendly and promising method to recycle aluminum electrolyte wastes and achieve resource utilization. [ABSTRACT FROM AUTHOR]

This perspective combines various expertise to develop and analyse the concept of technology cascade for recycling waste plastics with the goal of displacing as much fossil crude oil as possible. It thereby presents archetype recycling technologies with their strengths and weaknesses. It then combines them in various cascades to process a representative plastic mix, and determines how much (fossil) naphtha could be displaced and at which energy consumption. The cascades rely on a limited number of parameters that are fully reported in supplementary information and that were used in a simple and transparent spreadsheet model. The calculated results bust several common myths in plastic recycling, e. g. by prioritizing here recycled volume over recycling efficiency, and prioritizing circular industry over circular products . It unravels the energy cost of solvent-based recycling processes, shows the key role of gasification and the possibility to displace up to 70% of the fossil feedstock with recycled carbon, a recycling rate that compares well with that aluminium, steel or paper. It suggests that deeper naphtha displacement would require exorbitant amount of energy. It therefore argues for the need to complement recycling with the use of renewable carbon, e. g. based on biomass, to fully defossilise the plastic industry. [ABSTRACT FROM AUTHOR]

[Display omitted] • Recycling aluminium in a rotary furnace saves great environmental impacts. • Valorising the salt slag instead of landfilling improves LCA indicators by 5–25 %. • The discounted impacts from the secondary aluminium dominate the LCA results. • Other benefits are recovery of NMCs, ammonium sulphate and landfill prevention. • Metal Yield assumptions from 20 to 95 % change the GWP from −3.5 to −17 t CO 2 eq. Recycling aluminium in a rotary furnace with salt-fluxes allows recovering valuable alloys from hard-to-recycle waste/side-streams such as packaging, dross and incinerator bottom ash. However, this recycling route generates large amounts of salt-slag/salt-cake hazardous wastes which can pose critical environmental risks if landfilled. To tackle this issue, the metallurgical industry has developed processes to valorise the salt-slag residues into recyclable salts and aluminium concentrates, while producing by-products such as ammonium sulphate and non-metallic compounds (NMCs), with applications in the construction or chemical industries. This study aims to assess through LCA the environmental impacts of recycling aluminium in rotary furnaces for both salt-slag management routes: valorisation or landfill. It was found that this recycling process brings forth considerable net environmental profits, which increase for all the considered impact categories if the salt-slag is valorised. The main benefits arise from the production of secondary cast aluminium alloys, which is not unexpected due to the high energy intensity of aluminium primary production. However, the LCA results also identify other hotspots which play a significant role, and which should be considered for the optimisation of the process based on its environmental performance, such as the production of by-products, the consumption of energy/fuels and the avoidance of landfilling waste. Additionally, the assessment shows that the indicators for mineral resource scarcity, human carcinogenic toxicity and terrestrial ecotoxicity are particularly benefited by the salt-slag valorisation. Finally, a sensitivity analysis illustrates the criticality of the metal yield assumptions when calculating the global warming potential of aluminium recycling routes. [ABSTRACT FROM AUTHOR]

The aluminium industry for ship materials produces waste material that can pollute the environment. To protect the environment from material pollution, the aluminium waste recycling process can be used to develop ship material. This study aims to analyze the physical and mechanical characteristics of aluminium with magnesium, copper, and zinc addition. Several tests, such as chemical composition, tensile, and impact tests, will be conducted to ascertain the mechanical properties of aluminium alloy. Adding alloy material in the range of 0-10% resulted in various alloy element compositions. It can be analyzed that the aluminium contents decreased with the increase of alloy elements. The highest rise in alloy elements can be found in the addition of magnesium than in copper and zinc addition. Moreover, the mechanical tests showed that aluminium casting with magnesium, copper, and zinc additions influenced the mechanical properties of the aluminium alloy. It can be found that tensile strength and modulus of elasticity values improved with the increase of alloy addition. The addition of magnesium has better tensile properties than the addition of copper and zinc. In contrast, the impact resistance decreased with the addition of magnesium, making the alloy more brittle. [ABSTRACT FROM AUTHOR]

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In the recycling process, aluminum scraps, characterized by a considerable specific surface area, yield a remelt abundant in inclusions. While advanced melt purification systems proficiently extract hydrogen and large inclusions, micron-sized inclusions remain challenging to remove. Despite previous findings suggesting nominal effects of inclusions on the microstructure and properties of aged 7xxx-series plates, the products' airworthiness demands further improvement. This research aims to decipher the influence of micron-sized inclusions on the microstructure and properties of recycled 7xxx aluminum alloy. We prepared thin sheets of varied cleanliness and utilized SEM, EBSD, and TEM to characterize their microstructure at different heat treatment stages. Additionally, high-temperature tensile and bending properties, together with exfoliation corrosion behaviors, were examined. Our results point to the causative role of inclusions in localized dislocation accumulation post-rolling, which annealing can mitigate but not fully eliminate; however, a solid solution can effectively address this issue. The inclusions significantly disrupt the microstructure and properties of the annealed recycled sheet, but their impact on the solid solution-aged recycled sheet is minor. This study's findings can guide the high-end transformation of recycled aluminum alloy and lay a theoretical foundation for sustainable aluminum recycling.

Abstract In a bid to address the energy-intensive nature of primary aluminum production, this study explores the solid-state recycling of aluminum alloy 6082 chips through direct hot extrusion. Compacted at room temperature, chips were extruded at temperatures (350, 425, and 500 °C) and reduction ratios (6, 8.5, and 11) to optimize mechanical properties. Extensive analyses, including ANOVA and linear regressions, of strength, density, and microstructure revealed significant influences of those extrusion parameters. Optimizing these parameters within the study's aforementioned working ranges can impact the recycled material's strength; with a 36% reduction ratio increase and 20% temperature increase modestly reducing ultimate strength (2%), while a 20% temperature increase alone lowers yield strength more noticeably (9%). These findings highlight the potential for enhanced recycling and sustainable manufacturing.

The importance of mineral resources cannot be ignored in the country's economic and social development and is of vital significance in securing China's continued economic and social prosperity. Against the backdrop of the country's active promotion of the clean energy industry, the booming development of the photovoltaic industry has triggered a growing demand for its key raw materials, especially important metallic minerals. Based on the system dynamics theory, the article uses Vensim to construct a photovoltaic cell-key metal mineral simulation model to analyze the development of China's photovoltaic industry in depth and focuses on its far-reaching impact on the supply and demand relationship of key minerals. The results of the study show that (1) China's photovoltaic cells show strong growth; (2) recycling and technology substitution can significantly reduce the risk of copper and aluminum supply and demand imbalance; and (3) technology substitution is more effective than recycling in reducing the supply and demand imbalance of copper and aluminum. Based on the above-mentioned findings, the article puts forward corresponding policy recommendations. [ABSTRACT FROM AUTHOR]

Metal machining workshops generate a lot of metal chips, which pose both health and disposal challenges. Herein, for the first time, we demonstrate a novel process of reusing lathe-turning steel chips to manufacture high-compression strength Al alloy/steel composites. The process involves melting aluminium alloy onto the steel chips under vacuum and argon gas conditions. Clean and dried steel chips are packed inside a mould with a top layer of aluminium alloy pieces at three different quantity ratios of 80%Al/20% steel, 20%Al/80% steel and 50%Al/50% steel. The steel mould is then heated in a furnace at 650–700 °C until the aluminium metal melts. After a predetermined time of melting, argon gas is bubbled into the top layer (molten aluminium) of the mould while vacuum pumping is activated on the lower side of the mould (steel chips) for 5 min. The sample is allowed to cool within the mould. The composite containing 50%Al/50% steel has the highest mechanical properties with compression strength twice that of the other two samples. The microstructural observations revealed a good bonding between the steel chips and the Al alloy matrix. The study further presents the machinability of the samples, and it is seen that the composites behave like the aluminium matrix alloy during a turning operation and therefore do not require a special machining operation. It is shown that through this method, machining chips of steel can be recycled into high-compression strength metal–metal composites. These materials have the potential for high-compression strength applications such as machine supports and high-impact cushions. [ABSTRACT FROM AUTHOR]

• Recycled waste aluminum scraps were used to fabricate S-Al0@Fe0 with high e − capacity. • S-Al0@Fe0 with a three-layer structure had higher reactivity toward Cr(VI) than S-Fe0. • Cr(VI) removal capacity of S-Al0@Fe0 was 8.2 times higher than of S-Fe0. • S-Al0@Fe0 served as an electric cell to harness persistent and selective e − transfer. • S-Al0@Fe0 is a cost-effective and environmentally-friendly alternative to S-Fe0. Massive waste aluminum scraps produced from the spent aluminum products have high electron capacity and can be recycled as an attractive alternative to materials based on zero-valent iron (Fe0) for the removal of oxidative contaminants from wastewater. This study thus proposed an approach to fabricate micron-sized sulfidated zero-valent iron-aluminum particles (S-Al0@Fe0) with high reactivity, electron selectivity and capacity using recycled waste aluminum scraps. S-Al0@Fe0 with a three-layer structure contained zero-valent aluminum (Al0) core, Fe0 middle layer and iron sulfide (FeS) shell. The rates of chromate (Cr(VI)) removal by S-Al0@Fe0 at pH 5.0‒9.0 were 1.6‒5.9 times greater than that by sulfidated zero-valent iron (S-Fe0). The Cr(VI) removal capacity of S-Al0@Fe0 was 8.2-, 11.3- and 46.9-fold greater than those of S-Fe0, zero-valent iron-aluminum (Al0-Fe0) and Fe0, respectively. The chemical cost of S-Al0@Fe0 for the equivalent Cr(VI) removal was 78.5% lower than that of S-Fe0. Negligible release of soluble aluminum during the Cr(VI) removal was observed. The significant enhancement in the reactivity and capacity of S-Al0@Fe0 was partially ascribed to the higher reactivity and electron density of the Al0 core than Fe0. More importantly, S-Al0@Fe0 served as an electric cell to harness the persistent and selective electron transfer from the Al0-Fe0 core to Cr(VI) at the surface via coupling Fe0-Fe2+-Fe3+ redox cycles, resulting in a higher electron utilization efficiency. Therefore, S-Al0@Fe0 fabricated using recycled waste aluminum scraps can be a cost-effective and environmentally-friendly alternative to S-Fe0 for the enhanced removal of oxidative contaminants in industrial wastewater. [Display omitted] [ABSTRACT FROM AUTHOR]

A lack of fresh water is one of the most significant problems currently affecting humanity. Water scarcity also affects industries, with the mining industry being one of the most affected. One possible solution to water scarcity is the recirculation of water. Water in mining is usually treated with physicochemical methods, but in metallurgical processes, reagents are added, accumulate until reaching the point of saturation, and are often not successfully removed. In this sense, electrocoagulation has shown great efficiency in the treatment of organic contaminants, heavy metals, and metallic ions, and was applied in this study to eliminate ions and undesirable organic compounds present in mining–metallurgical process water. Furthermore, this process has shown great efficacy in relation to toxic metals like arsenic because their presence reduces the efficiency of other processes such as flotation. In this study, two types of electrodes were used: stainless steel and aluminum. The best results were achieved with stainless steel electrodes, which were able to eliminate 90% of copper ions in water. The turbidity of the water during the process was measured to determine the amount of solid present in the water, and a reduction of around 95% was observed when using aluminum electrodes. The sedimentation of clots occurred in two stages: Firstly, the coagulant was formed to trap organic matter as its size increased, until a particle size that was sufficient for settling was achieved. A zero-order kinetic model was fit for this stage of the process. Secondly, the formed clots continued to settle, and a second-order kinetic model was fit for this stage. Flotation tests were carried out on the process and electrotreated water to evaluate the recovery of Zn, Pb, Ag, and Au. An increase of 1.5% was found for gold, and an increase of 2% was found for silver, while a significant improvement was identified for zinc, augmenting recuperation by 30% when electrotreated water was used. For lead, no considerable change in recovery was observed in either form of water. The formed clots were analyzed using Scanning Electronic Microscopy, and we found that metal ions were trapped in the clots. This study demonstrates the potential of electrocoagulation for clarifying mine water, which is ordinarily very difficult to clarify. [ABSTRACT FROM AUTHOR]

When processed conventionally, aluminum-bronze alloys with high mechanical strength require machining after the raw state of fusion, and the waste (chips), if not reused, can cause problems for the environment and costs for the company. Therefore, this article proposes an alternative for recycling aluminum bronze through the new route via Powder Metallurgy (PM), analyzing the resulting microstructure. This study compares the microstructures of the aluminum bronze derived from extraction (the samples received - SR) and the state after the powder metallurgy (PM) process with the addition of vanadium carbides (VC). The study also analyzes the distribution of VC in the microstructure of the PM composite as well as the influence of the TQ30 heat treatment on this composite. For the PM process, aluminum alloy and bronze chips were ground together with vanadium carbide (VC) in a high-energy mill for 50 hours. The powders obtained were pressed uniaxially (400 MPa) to achieve good compaction. The samples were then sintered (900°C/1h), water quenched (900°C/2h), and subjected to treatment according to the TQ30 standard, which, in addition to the previous treatments, also includes tempering at 500°C for 2 hours (ASTM B150/B150M-12 standard). The microstructure observed in the SR samples was martensitic (in needles), with secondary phases dispersed in the matrix. On the other hand, the microstructure of the PM samples showed equiaxed grains of the alpha phase (κ), as well as the secondary phases kapa (κ) and beta line (β'), in contrast to the needle-shaped microstructure of the conventional melting process. [ABSTRACT FROM AUTHOR]

The potential to subsidize the development of areas furnished with ores is essential for producing supplies, services, and infrastructure that get a better social life quality. Bauxite mining is the foremost open-cast mining and bauxite is the only material for manufacturing aluminum metals and is used as a prominent industrial raw material. Demand for bauxite has grown enormously because of increased population and economic growth as it is required for the production of many other metals. A huge amount of bauxite residues are produced during aluminum production from bauxite ore which tremendously influences the environment and public health. Production of waste residues from bauxite ore leads to diminishing soil productivity and influences farming food yields. Soil and water are also contaminated by the addition of heavy metals, iron oxide, and aluminum hydroxide, which can prejudice public health. Microorganisms degrade and detoxify the pollutants into a nontoxic organic form that is helpful to the environment. Bioremediation has been a promising method to remove contaminants by using microorganisms. This enables the adsorption, accumulation, degradation, and utilization of emerging contaminants as nutrient resources by microbial communities for their sustenance. Sustainable management of bauxite mining and recovery of metals from wastes are mainly indispensable in this high time. This review article evaluates the effect of bauxite waste residues on the environment and its consequences on human health; it also emphasizes the biological remediation strategy for the remediation of contaminated mining areas and focuses on the sustainable management of bauxite waste residues. [ABSTRACT FROM AUTHOR]

In a bid to address the energy-intensive nature of primary aluminum production, this study explores the solid-state recycling of aluminum alloy 6082 chips through direct hot extrusion. Compacted at room temperature, chips were extruded at temperatures (350, 425, and 500 °C) and reduction ratios (6, 8.5, and 11) to optimize mechanical properties. Extensive analyses, including ANOVA and linear regressions, of strength, density, and microstructure revealed significant influences of those extrusion parameters. Optimizing these parameters within the study's aforementioned working ranges can impact the recycled material's strength; with a 36% reduction ratio increase and 20% temperature increase modestly reducing ultimate strength (2%), while a 20% temperature increase alone lowers yield strength more noticeably (9%). These findings highlight the potential for enhanced recycling and sustainable manufacturing. [ABSTRACT FROM AUTHOR]

Direct recycling of aluminum waste is crucial in sustainable manufacturing to mitigate environmental impact and conserve resources. This work was carried out to study the application of hot press forging (HPF) in recycling AA6061 aluminum chip waste, aiming to optimize operating factors using Response Surface Methodology (RSM), Artificial Neural Network (ANN) and Genetic algorithm (GA) strategy to maximize the strength of recycled parts. The experimental runs were designed using Full factorial and RSM via Minitab 21 software. RSM-ANN models were employed to examine the effect of factors and their interactions on response and to predict output, while GA-RSM and GA-ANN were used for optimization. The chips of different morphology were cold compressed into billet form and then hot forged. The effect of varying forging temperature (Tp, 450–550°C), holding time (HT, 60–120 minutes), and chip surface area to volume ratio (AS:V, 15.4–52.6 mm2/mm3) on ultimate tensile strength (UTS) was examined. Maximum UTS (237.4 MPa) was achieved at 550°C, 120 minutes and 15.4 mm2/mm3 of chip's AS: V. The Tp had the largest contributing effect ratio on the UTS, followed by HT and AS:V according to ANOVA analysis. The proposed optimization process suggested 550°C, 60 minutes, and 15.4 mm2 as the optimal condition yielding the maximum UTS. The developed models' evaluation results showed that ANN (with MSE = 1.48%) outperformed RSM model. Overall, the study promotes sustainable production by demonstrating the potential of integrating RSM and ML to optimize complex manufacturing processes and improve product quality. [ABSTRACT FROM AUTHOR]

When it comes to sustainability, aluminium has numerous aspects. This presents an opportunity to advance the metalworking industry towards a circular economy. However, a significant obstacle is the presence of high levels of elemental contamination in vast quantities of post-consumer scrap. This must be considered in the design of alloys that are more sustainable. In this regard, the current study investigates the effect of copper addition on recycled aluminum chips. The microstructure, mechanical characteristics, tribological behavior, and electrical conductivity has been examined. The wear experiments were carried out at various loads, times, and spindle speeds. The results showed that increasing the copper content by up to 6 wt.% increased the number of grain boundaries and their constituents. Furthermore, large agglomerates have formed in some areas, most notably in the 10 wt.% Cu sample. In addition, the XRD analysis indicates a grain refining effect. As a result, 8 wt.% Cu sample exhibits optimal behavior, as its uniform dispersion aids in enhancing the mechanical and tribological characteristics of composites. A moderate sufficient wear resistance and electrical conductivity merged with good mechanical performance, open the opportunity to an effective approach of recycling aluminium scrap and incorporating it into a product with sufficient quality and cost-effective negotiations. [ABSTRACT FROM AUTHOR]

• Experimental investigation on regeneration of zeolite 13X is carried out. • Material like aluminum, stainless steel, and aluminum oxide nanoparticles are used. • Drying kinetic analysis for zeolite desorption with various materials is investigated. • Integration of materials with zeolite 13X enhanced the desorption rate. • Drying constants for semi-theoretical and empirical models are presented. The effect of adding metal pieces in the adsorbent bed for enhancing the effective thermal conductivity and drying kinetics is investigated for the Zeolite 13X bed. Aluminum, stainless-steel pieces ranging in size from 1.5 cm to 2 cm, and aluminum oxide nanoparticles are chosen, and the total weight added to the bed is approximately 2 % of the adsorbent weight. The different semi-theoretical drying models like Lewis, Page, Logarithmic, Henderson, and Pabis and empirical models like Weibull and Gaussian model are used for the analysis. Adsorption and desorption of Zeolite 13X-water integrated with various metal pieces revealed a decrease in the adsorption capacity of adsorbents with metal pieces and increased bed moisture content for powdered aluminum oxide. It can be noticed that the desorption process was improved by including the metal pieces in the adsorbent bed.; Desorption rates range from 19.54 % for the bed mixed with straight aluminum pieces and 21.43 % for the bed filled with stainless steel. The desorption rates for the bed containing nanoparticles of aluminum oxide and spiral aluminum pieces are 20.48 % and 22.21 %, respectively. The experimental investigation on efficiency enhancement revealed that the desorption process of an adsorbent bed with straight aluminum pieces increased efficiency by 12.38 %, while the bed with aluminum oxide and stainless steel increased efficiency by 17.75 % and 23.20 %, respectively. The effectiveness of an adsorbent bed with spiral aluminum pieces is enhanced by 27.68 %. The drying kinetics analysis of zeolite 13x regeneration using semi-theoretical and empirical models which showed good agreement with experimental results. [Display omitted] [ABSTRACT FROM AUTHOR]

The recycling of agro‐waste as complementary reinforcements has received significant recognition in the development of aluminium matrix composites. Hence, this study examines the corrosion behavior of Al6063 reinforced with hybrid SiC/PKSA (palm kernel shell ash) particles. Through various ratios of SiC and PKSA particles in Al6063 alloy, composites were fabricated by double stir casting. Samples were cut and metallographically prepared for 1 M H2SO4 solution corrosion experiments. Gravimetric, potentiodynamic polarization and electrochemical impedance spectroscopic analyses were employed. The composites corroded initially at relatively high rates, gradually declining during long immersion times in the acidic solution. The intersection of reinforcements at the general surfaces of the composites where flawed oxide skins predominate acted as active sites for corrosion initiation. From potentiodynamic polarization studies, the corrosion currents increased with time for all specimens, with A9 being 1075.65 μA/cm2 at 72 h as against 857.99 μA/cm2 at 24 h of measurement. The corrosion potentials for all the specimens hovered around −654.00 to −647.22 mV. Bode plots revealed similar electrochemical reactions over all the substrates' surfaces. The relative corrosion resistance by the specimen depends on the oxide films' nature as the cathodic interfacial reinforcements dropped off into the acidic environment. [ABSTRACT FROM AUTHOR]

Aluminum alloys possess excellent mechanical properties and corrosion resistance that make them desirable for applications in the automotive industry. Additionally, aluminum is infinitely recyclable with excellent recovery rates. However, recycling aluminum leads to the accumulation of impurities such as iron and copper. These impurity elements decrease the ductility and fatigue life of secondary aluminum, which limits the use of recycled alloys for structural applications. Casting is one of the most efficient methods used to fabricate aluminum alloys due to a low melting point and relatively high fluidity. This study executed a thorough analysis of the processing-structure-property relationships of two commercial secondary alloys: 383.1 and 356.1. Additionally, one custom recycled aluminum alloy was designed and prepared for permanent mold casting. Metallographic samples of each alloy were prepared for microstructural analysis. Furthermore, ASTM subsize tensile bars were machined for tensile testing. The results obtained from the permanent mold casting trials are promising for structural application of new secondary alloys. [ABSTRACT FROM AUTHOR]

Recycling of aluminum (Al) alloys is critical to meet the demands of global net zero emission targets. The major challenge in the recycling of Al alloys is the presence of a higher content of iron as an impurity in Al alloy scraps, which deteriorates the mechanical properties of recycled alloys. In the present work, Al-7%Si alloys and Al-7%Si-2Fe alloys were cast at three different superheat temperatures to study the effect of superheat on the formation of iron intermetallic particles in these alloys. Microstructure–mechanical properties correlations were carried out using SEM-EDS and tensile testing of the alloys. 3D x-ray computed tomography (XCT) results show that the β-phase intermetallic particles were observed to be large and platelet-shaped in the Al-7Si-2Fe alloy cast at 700°C, while these particles appeared to be finer and uniformly distributed throughout the sample in the alloy cast at 900°C. XCT results show the presence of large shrinkage porosity in the Al-7Si-2Fe alloy cast at 700°C, due to the presence of large intermetallic particles which hinder the flow of molten metal during solidification of the alloys. Tensile test results show that the addition of 2% iron resulted in a significant reduction in the elongation of the alloy at all superheat temperatures. [ABSTRACT FROM AUTHOR]

In view of the increasing scarcity of bauxite resources in China, the high energy consumption and high pollution of electrolytic aluminum, and the requirements for energy conservation and environmental protection, aluminum recycling and high-value utilization of its derivatives have evolved into a crucial development requirement for the aluminum industry in the future. As an important part of the development of recycled aluminum resources, the high-value application of scrap aluminum cans has always been a hot research topic in various recycled aluminum processing enterprises and scientific research units. The traditional regeneration system of waste cans includes a series of complex technological processes such as pretreatment, paint removal, smelting system and casting system, which is difficult to control in the middle of the process. Most of the recycled scrap aluminum cans are cast and downgraded for later use, except for a part of them used as alloy materials for new cans. In this paper, combined with the research on the preparation of metal aluminum alkoxide, combined with recrystallization heat conduction to further study the effective dissolution or adsorption how to remove impurity elements to obtain highpurity aluminum alcohol salt mechanism research, and thermal effect of alcohols with different carbon chains on the synthesis of high-purity aluminum alkoxide was further investigated. Moreover, the changes in morphology and pore size distribution of hydrolyzed alumina precursor materials under different hydrothermal temperature conditions were discussed by means of the alkoxide hydrolysis-sol-gel process. Eventually, the aluminum alkoxide was obtained by the reaction of waste cans with isopropanol and heavy crystal thermal conductivity, and the high-purity aluminum alkoxide was purified by vacuum distillation. Under the hydrothermal condition of 160°C, the high-purity alumina material with a purity of 99.99% and an original crystal size of 200nm was prepared. [ABSTRACT FROM AUTHOR]

An as-cast aluminum billet with a diameter of 100 mm has been successfully prepared from aluminum scrap by using direct chill (DC) casting method. This study aims to investigate the microstructure and mechanical properties of such as-cast billets. Four locations along a cross-section of the as-cast billet radius were evaluated. The results show that the structures of the as-cast billet are a thin layer of coarse columnar grains at the solidified shell, feathery grains at the half radius of the billet, and coarse equiaxed grains at the billet center. The grain size tends to decrease from the center to the surface of the as-cast billet. The ultimate tensile strength (UTS) and the hardness values obtained from this research slightly increase from the center to the surface of the as-cast billet. The distribution of Mg, Fe, and Si elements over the cross-section of the as-cast billet is inhomogeneous. The segregation analysis shows that Si has negative segregation towards the surface, positive segregation at the middle, and negative segregation at the center of the as-cast billet. On the other hand, the Mg element is distributed uniformly in small quantities in the cross-section of the as-cast billet. [ABSTRACT FROM AUTHOR]

Spent carbon cathode (SCC) is a hazardous waste from the aluminum electrolysis industry. It is commonly used as a carbon source in the current disposal and recovery strategies, such as combustion, or as a reductant for smelting. The novelty of this study is to propose a strategy for recycling SCC as a graphite resource and to investigate the unique structural characteristics and adsorption properties of graphene oxide produced from this low temperature graphitized carbon. The adsorption kinetics and isotherms of SCC-GO on methylene blue (MB) were studied and compared with the GO prepared from natural flake graphite (NFG) and artificial graphite (AG). The results show that SCC-GO exhibits the highest adsorption rate and adsorption capacity (647.83 mg/g) for MB, which is much higher than NFG-GO (451.22 mg/g) and AG-GO (533.12 mg/g). The analysis of the spectroscopy and morphology confirmed that SCC-GO has a high degree of crystal defects, oxidation, and surface wrinkle. Overall, this study reveals the unique structure of SCC-GO and highlights its significant scientific and application potential as an ultra-low temperature graphitized carbon. This research is also significant for recycling aluminum electrolytic cathode solid waste in the form of a graphite source. [ABSTRACT FROM AUTHOR]